1. Field of the Invention
The present invention relates to a rotary vane pump with packing means for the housing components.
2. Description of the Prior Art
FIG. 1 is a side cross sectional view of the conventional pump device and FIG. 2 is a front cross sectional view taken along the line II--II of FIG. 1. In the FIGS. 1 and 2, an end frame (1) is the bracket of an AC generator for a car (not shown). A shaft (2) is driven by the AC generator and is supported by the end frame through a bearing (3). A rotor (4) is fixed to the shaft (2) by a spline fitting. A plurality of vanes (5) are inserted into radial grooves of the rotor (4) so as to be slidable in the radial direction of the rotor (4). A housing (6) has a cylindrical inner wall which is eccentric to the center of the rotor (4) and contains the rotor (4) and the vanes (5). A plate (7) is placed between the end frame (1) and the housing (6). A fitting bolt (8) fastens the housing (6) and the plate (7) to the end frame (1). A packing (9) is used to seal the housing (6) and the plate (7) in a hermetic condition and a packing (10) is also used to seal the plate (7) and the end frame (1) in a hermetic condition. An oil seal (11) is fitted to the end frame (1) and is in contact with the circumference of the shaft (2) to keep the operation chamber of a pump device in a hermetic condition. An intake port (13), an exhaust port (14) and an oil feeding port (15) are formed in the housing (6) to be respectively connected to a vacuum tank, an oil pan and an oil pump (not shown).
The operation of the conventional pump device will be described. When the shaft (2) is rotated in the direction of the arrow mark in the FIG. 2, the vanes (5) are projected outwards by the centrifugal force given to the vanes and are rotated in sliding contact with the inner wall of the housing (6) whereby a vacuumed air in the vacuum tank is sucked from the intake port (13) and the air thus sucked is discharged through the exhaust port (14) to perform a pumping operation. Oil fed through the oil feeding port (15) into the housing (6) gives a lubrication for the sliding movement of the vanes (5) and the rotor (4) and is discharged into the oil pan (not shown) through the exhaust port (14).
In the conventional pump device, the packings (9) and (10) are respectively fitted to rectangular grooves in corss section formed on the side surface of the plate (7) and the housing (6) and are respectively clamped by the side surface of the adjacent end frame (1) and the housing (6). In a case that the packings (9), (10) are fitted to the grooves, however, the packings are often detached from the grooves because means for fixing the packing is not provided to result in low efficiency in assembling operation. When an O-ring packing is used, the inner diameter of the groove is normally formed smaller than that of the O-ring packing whereby the packing (9) or (10) easily rises from the groove. In this case, the packing (9) or (10) is fitted by a part associated with the groove to cause air leakage.